Ray Hyman’s categorical imperative is “Do not try to explain something until you are sure there is something to be explained.” These researchers believe there is something to be explained. They think chiropractic has proven clinical benefits and they are trying to find the underlying physiological mechanisms. They think they have found something with their advanced imaging procedures, but the dead salmon study and Satel and Lilienfeld’s book Brainwashed have taught us that neuroimaging studies can be misleading and must be interpreted with great caution.

They say chiropractic is “one of the manipulative therapies initiated by Daniel David Palmer.” I didn’t know he initiated any other manipulative therapies; I wonder what they were. They argue that chiropractic is widely used and is legislated in the U.S. and in over 20 other countries. So what? That’s not evidence that it works. They say chiropractic spinal manipulation is “considered one of the main treatment techniques for neuro-muscular-skeletal problems.” Considered by whom? Which neuro-muscular-skeletal problems, exactly?

Experimental design

Subjects were volunteers who responded to a poster on a university campus. 20 patients with low back pain were divided into three groups (normal, sacral base anterior and sacral base posterior) by pressure testing in Activator Methods. 9 were classified into the SB anterior group, 11 into the SB posterior group, and none into the normal group. Subjects received chiropractic spinal manipulation (CSM) depending on the results of pressure testing. They don’t describe what the chiropractic treatment was; but they state that all treatments were performed by the same chiropractor who was “an advanced proficiency rated doctor of Activator Methods,” so I think we can assume the treatments were activator treatments. Activators are spring-loaded instruments that provide a variable impulse to a localized area. They provide a “kinder, gentler” chiropractic for patients who are wary of the traditional “back-cracking” manipulations. Activator methods have not been scientifically validated, and they are not the most characteristic chiropractic treatment; the very name chiropractic is derived from “hands-on,” not gadgets-on. Only 70% of chiropractors use activators, and only 24% of patients get that treatment.

The description of what they did is confusing, to say the least. They start out talking about 20 subjects with low back pain, then they say subjects had cervical pain and shoulder stiffness. 20 patients with low back pain somehow morphed into 15 with neck pain who were “first assigned for MRI examination of the cervical region” [the neck], then 3 were excluded because they had disc problems. So they ended up with only 12 subjects. Although the first mention of MRIs refers to the neck, the images shown in the study write-up are MRIs of the low back.

The experimental design was a crossover study comparing scan results in the same patient with and without CSM.

Results

They found that chiropractic treatment produced:

Apparent angle changes on MRI in most but not all subjects

Increased glucose metabolism in certain areas of the brain and decreased metabolism in other areas

Subjective improvement with lower visual analog scores (VAS)

Changes in cervical muscle tone

Reduced salivary amylase values

Deactivation of the cerebellar vermis, which is considered to be playing a role in pain perception and is thought to be involved with the autonomic nervous system.

Activation of the cingulate cortex and inferior prefrontal cortex, which are known to be involved in the generation of autonomic responses.

They say the observed angle changes “clearly demonstrated that this phenomenon is caused by balancing effect of CSM on the alignment of the lumbar spine and the sacrum.” Sorry, but I don’t think it clearly demonstrates anything of the sort.

They think they have demonstrated effects of CSM both in peripheral structures and in the central nervous system, providing a mechanism that would explain the efficacy of CSM. I don’t.

Problems

There are a lot of things that bother me about this study:

They are trying to show “how” CSM works without first showing “that” it works.

The method they chose to represent chiropractic, activator method, is not representative and has not been validated.

There were only 12 subjects.

They didn’t use another treatment as a control.

The write-up is hopelessly confused, with low back pain morphing into neck pain and shoulder stiffness.

CSM procedures are not described. We don’t know what was actually done.

They give no rationale for measuring salivary amylase and no explanation of what they think reduced levels might mean.

There is no way to know what the changes on MRI and PET imaging really mean. MRIs are only pictures that require careful interpretation and clinical correlation: an abnormal MRI can indicate spine disease but MRIs are also abnormal in a significant percentage of normal people who don’t have back pain. PET scans are only an indirect indication of what is happening in the brain, highlighting variable areas that could represent either activation or repression of some function. This may not be another dead salmon study, but it may be just as meaningless.

Conclusion

In my opinion, this study amounts to junk science and a fishing expedition. They have used sophisticated new toys to produce questionable findings and they have over-interpreted the meaning of the data.

The last sentence in the report was “Further neuroimaging studies are needed on effects of CSM.” I disagree. I think they would be a waste of time, just like this study.